Modern building construction utilizes fire resistive walls and floors to confine the spread of fires; yet mechanical and electrical piping, electrical cable, and duct work penetrate, and construction gaps, expansion joints, and curtain wall openings may occur in these assemblies. Unsealed openings and penetrations diminish the effectiveness of fire rated walls and floors, threatening life, property and operations by allowing smoke and flames to pass unchecked through the building.
A fire stop must maintain its sealing properties not only in the initial stages of a fire, but also as it heats and burns as the fire matures. In essence, this means that the fireproof seal must contain an ingredient or ingredient combination which can replace any volume lost as the polymeric base and/or fillers and extenders are used up during a fire or flash fire condition. This property of compensating that lost mass is commonly referred to as intumescence.
Elastic fireproof materials employing an elastomer, vulcanizing agents and an intumescent mineral are disclosed in U.S. Pat. No. 4,266,039 (Hons-Olivier, et. al.). Hons-Olivier, et al, teaches the use of nondehydrated vermiculite mineral as the intumescent. Repeated trials incorporating this mineral in a compressible composition resulted in spongy structures that either failed to pass the ASTM E-814 fire test, or failed to exhibit sufficient softness as measured by compression-deflection. Vermiculite has insufficient expansion and tends to produce a composition with a friable char. A prime requirement to survive the ASTM E-814 fire test is the ability of the composition to intumesce and form a char strong enough to withstand the hose stream test. Increasing the quantity of vermiculite to obtain better expansion is deleterious to char strength and softness.
It is therefore an object of this invention to provide an effective, compressible, fireproof seal for use during flame and heat exposure and especially to provide for improved resistance during the subsequent impact, erosion and cooling effects of a hose stream.